In the United States, how many percentages of schools have uniform by the year of 2009-2010?

The answer to this question is...
10 percent of high schools in the United States required uniforms
19 percent of middle schools
22 percent of elementary schools


We also found out an interesting fact about the percentage. It looks like it differs by where the school is.
35 percent of city schools reported requiring students to wear uniforms
19 percent of suburban schools
10 percent of schools in towns
9 percent of rural schools

"Uniforms for Public School Students? The Debate Continues as They Become More Popular - The Boston Globe." BostonGlobe.com. Web. 23 July 2015. https://www.bostonglobe.com/metro/regionals/south/2014/02/20/uniforms-for-public-school-students-the-debate-continues-they-become-more-popular/btIYoFLoizOkFpXrdEUScK/story.html#.

Are there any universities in Japan which students must wear certain uniforms?

The answer is... Yes!
We found out that there are more than 20 universities that have school uniforms. However, all the schools' students are not forced to wear them everyday. They wear certain uniformsonly in special occasions like entering and graduation ceremonies and so on.

"制服のある大学・短期大学 - NAVER まとめ." NAVER まとめ. Web. 23 July 2015. http://matome.naver.jp/odai/2134858283517635001?page=2.

Do uniforms improve performance?

Well, we could not find the exact answer to this question. That's because there are many researches about it and many results come up.
 YES... In 2007, researchers found out that only one of the top-performing 100 state schools in England was non-uniform.
NO... More than 40 academies in 2010 failed to reach the government's "floor target" of 30% of pupils with five A*-C GCSEs including maths and English, even though they have school uniforms.

The Guardian. Web. 23 July 2015. http://www.theguardian.com/education/2011/jan/18/school-uniform-results.

Do school uniforms make campus safer?

We found that in California, in 1994, began requiring school uniforms to reduce the number of crimes. The result is... it actually made the school campus safer! Five years later, the crime rate in a certain district decreased by 91%. It is said that especially sex offences decreased by96%.

"Reasons Why Schools Should or Shouldn't Use Uniforms." Everyday Life. Web. 23 July 2015. <http://everydaylife.globalpost.com/reasons-schools-should-shouldnt-use-uniforms-16854.html>.

From what year did the percentage of schools with uniforms increase significantly in the US?

Recent researches have shown that the answer to this question is... betweeen 2013-2014, and between 2011-2012. The percentage of public schools which have school uniforms increased by 13 to 19 percent.

Web. 23 July 2015. <https://nces.ed.gov/fastfacts/display.asp?id=50>.

1. Does wearing uniform really reduce the number of crime and violence? 2. If so, How much percentage did it lessen?

 We found a very interesting fact about these questions. According to Phoenix
school officials in California, attendance and test scores seemed to improve, incidents of students fighting decreased by 50%, student crimes decreased by 36% and student suspensions decreased by 32% after they enacted a uniform policy. Although there are many opinions about this topic, this is a fact that we can trust.

"SocialPC." Uniforms In Public School. Web. 22 July 2015. http://www.socialpc.com/SocialIssues/Uniforms-In-Public-School.html.

Name five big population states in America with the most students who wear school uniforms.

 We could not find the exact answer to this question, but we found an interesting fact.
Nearly one in five public schools in America mandated uniforms in 2010, up from one in eight a decade earlier.  It seems that having uniforms is not an unusual thing for public schools in America nowadays. This means that stater which have many public schools tend to have many students who wear school uniforms.

Toppo, Greg. "What to Wear? Schools Increasingly Making That Decision." USA Today. Gannett, 18 Aug. 2013. Web. 22 July 2015. http://www.usatoday.com/story/news/nation/2013/08/18/more-school-uniforms/2662387/.